diff --git a/includes/class-wc-install.php b/includes/class-wc-install.php
index db3acb3b242..9f1ba36a1f3 100644
--- a/includes/class-wc-install.php
+++ b/includes/class-wc-install.php
@@ -443,8 +443,8 @@ CREATE TABLE {$wpdb->prefix}woocommerce_sessions (
   session_key char(32) NOT NULL,
   session_value longtext NOT NULL,
   session_expiry bigint(20) NOT NULL,
-  UNIQUE KEY session_id (session_id),
-  PRIMARY KEY  (session_key)
+  PRIMARY KEY  (session_key),
+  UNIQUE KEY session_id (session_id)
 ) $collate;
 CREATE TABLE {$wpdb->prefix}woocommerce_api_keys (
   key_id bigint(20) NOT NULL auto_increment,